FIG. 15 is a partial cross-sectional view of a known magnetic sensing element, i.e., spin-valve thin film element, cut from the direction parallel to a surface facing a recording medium.
Referring to FIG. 15, a base layer 1 is composed of Ta, and a seed layer 2 composed of a metal having a body-centered cubic (bcc) structure, for example Cr, is disposed on the base-layer 1.
A multilayer film T is deposited on the seed layer 2. In the multilayer film T, a free magnetic layer 3, a nonmagnetic layer 4, a pinned magnetic layer 5, an antiferromagnetic layer 6, and a protective layer 7 are disposed in that order.
The free magnetic layer 3 is composed of a Heusler alloy such as Co2MoAl, the nonmagnetic layer 4 is composed of Cu, the pinned magnetic layer 5 is composed of CoFe, the antiferromagnetic layer 6 is composed of PtMn, and the protective layer 7 is composed of Ta.
An exchange coupling magnetic field is generated at the interface between the antiferromagnetic layer 6 and the pinned magnetic layer 5, thereby pinning the magnetization of the pinned magnetic layer 5 in the height direction (in the Y direction in the figure).
Hard bias layers 8 composed of a hard magnetic material such as CoPt are disposed at each end of the free magnetic layer 3. The upper parts, the lower parts, and the ends of the hard bias layers 8 are insulated by an insulating layer 9. The magnetization of the free magnetic layer 3 is aligned in the track width direction (in the X direction in the figure) by a longitudinal bias magnetic field from the hard bias layers 8.
When an external magnetic field is applied to the magnetic sensing element shown in FIG. 15, the magnetization direction of the free magnetic layer 3 is relatively changed to that of the pinned magnetic layer 5. Consequently, the resistance of the multilayer film is changed. Under a constant sense current, such a change in resistance is detected as the change in voltage, thus detecting the external magnetic field.
Japanese Unexamined Patent Application Publication No. 8-250366 discloses a magnetic sensing element including the free magnetic layer 3 composed of a Heusler alloy. The free magnetic layer 3 is disposed on the seed layer 2 composed of a metal having the bcc structure.
According to the above patent document, the free magnetic layer 3 composed of a Heusler alloy is disposed on the seed layer 2 composed of a metal having the bcc structure, and consequently, the free magnetic layer 3 can be formed as an adequately crystallized thin film.
However, if it is essential that the free magnetic layer 3 composed of a Heusler alloy is disposed on the seed layer 2 composed of a metal having the bcc structure, a pinned magnetic layer 5 composed of a Heusler alloy cannot be formed between the nonmagnetic layer 4 and the antiferromagnetic layer 6. The reason for this is that the nonmagnetic layer 4 and the antiferromagnetic layer 6 generally have the face-centered cubic (fcc) structure.
For the same reason, a bottom spin-valve giant magnetoresistive (GMR) magnetic sensing element cannot be formed. In the bottom spin-valve GMR magnetic sensing element, the antiferromagnetic layer 6, the pinned magnetic layer 5, the nonmagnetic layer 4, and the free magnetic layer 3 are sequentially deposited from the bottom to form a multilayer film.